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Death toll in Thailand floods crosses 500

The death toll from Thailand's worst flooding in half a century has climbed past 500, as advancing pools of polluted black water threatened Bangkok's underground railway system.

As new evacuations were ordered in the sprawling capital, the latest district added to the government's evacuation list was Chatuchak, home to a major public park and an outdoor shopping zone that is a major tourist attraction.

The Chatuchak Weekend Market was open, but missing many vendors and customers on Sunday as floodwaters poured past the market's eastern edge for a second day.

The evacuations are not mandatory, and most people are staying to protect their homes and businesses. But the orders illustrate how far flooding has progressed into the city and how powerless the government has been to stop it.

Chatuchak is just a few miles north of Bangkok's central business district, which still is dry. On Sunday, cars drove through a flooded road underneath Chatuchak's Mo Chit Skytrain station, the northernmost stop on Bangkok's elevated train system.

Floodwaters also reached roads at three metro stops in northern Bangkok, though both mass transit networks are functioning normally.

Renate Vuuren of World Vision, the humanitarian organisation, told Al Jazeera that people in Bangkok were on edge. "It is difficult to bring aid because of transport and access problems," she said.

"In the larger part of the country, at least a third of the country has been inundated, and in Bangkok it is almost oozing into the city."

Health is a "very big concern" for everyone, as a result of the carcasses and the accumulation of garbage, she said.

Heavy rainfall

Large swaths of Thailand have experienced heavy rainfall and flooding since late July, leaving 506 people dead, according to the latest government statistics.

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Most victims have drowned, while a handful died from flood-related electrocutions. No deaths have been reported in Bangkok.

The nearby province of Ayutthaya, which has been submerged for more than one month, has the highest toll with 90 reported dead.

Floodwaters have begun receding in some provinces north of the capital, and a major clean-up is planned in Ayutthaya this week.

But the run-off has massed around Bangkok and completely submerged some of the city's outer neighbourhoods.

Also in Chatuchak, water has begun approaching a main road near the Mo Chit bus terminal, a major gateway to northern Thailand.

The bus station and roads in the area remained open, Uthaiwan Kaewsa-ard, the traffic police chief, said.

In the last few days, floods have also begun moving southward in adjacent Lad Phrao, a district full of office towers, condominiums and a popular shopping mall.

On Friday, workers completed a 6km flood wall made from massive, hastily assembled sandbags to divert some of the water flowing towards central Bangkok.

But large amounts of water are already beyond that wall, and officials say that besides a network of canals and underground drainage tunnels, there are no more barriers preventing water from pushing south into the heart of the city.